Subaru Rear Trailing Arm Explained: Key Specifications, Features, and Common Uses

Types of Subaru Rear Trailing Arms

A Subaru rear trailing arm is a critical component of the vehicle's rear suspension system, responsible for maintaining proper wheel alignment, controlling lateral and longitudinal movement of the rear wheels, and ensuring optimal handling and ride stability. As a key link between the chassis and the rear suspension assembly, trailing arms influence everything from cornering precision to ride comfort and tire wear.

This guide explores the two primary types of Subaru rear trailing arms—adjustable and solid—highlighting their design, benefits, limitations, and ideal applications to help you make an informed decision based on your driving needs and performance goals.

Adjustable Rear Trailing Arms

Engineered for performance tuning, adjustable trailing arms allow precise control over rear wheel alignment and axle positioning.

Advantages

• Allows fine-tuning of rear toe and camber settings
• Enables customization for track, drift, or aggressive street driving
• Compensates for wear or modifications in the suspension system
• Ideal for lowered or modified vehicles requiring realignment

Limitations

• Requires professional alignment after adjustments
• Potential for loosening if not properly torqued
• Higher cost compared to solid arms
• Necessitates tools and mechanical knowledge for setup

Best for: Performance enthusiasts, track-day drivers, modified Subarus, and alignment tuning

Solid Rear Trailing Arms

Factory-style fixed arms designed for durability and consistent performance without the need for adjustment.

Advantages

• High structural rigidity and strength
• Maintenance-free operation once installed
• Resistant to loosening under heavy loads or off-road use
• Cost-effective and widely available as OEM replacements

Limitations

• No adjustability for alignment changes
• May require aftermarket camber kits for modified suspensions
• Limited flexibility for performance tuning

Best for: Daily drivers, OEM replacements, off-road vehicles, and those seeking reliability and simplicity

The choice between adjustable and solid rear trailing arms ultimately depends on your driving style, vehicle modifications, and long-term goals. Adjustable arms offer versatility and precision for drivers who want to optimize handling dynamics, especially in performance or modified setups. In contrast, solid arms provide a reliable, no-fuss solution perfect for stock or rugged-use vehicles where consistency and strength are paramount.

Expert Tip: When installing adjustable trailing arms, always use a torque wrench to secure the mounting bolts and schedule a professional alignment afterward. Improper adjustment can lead to uneven tire wear, unstable handling, or premature component failure.

Whether you're enhancing your Subaru for spirited driving or maintaining it for dependable daily performance, understanding the role and differences between these trailing arm types ensures you can maintain optimal suspension geometry, improve vehicle dynamics, and extend the life of your tires and suspension components.

Function of Subaru Rear Trailing Arm

The Subaru Legacy rear trailing arm is a crucial component of the vehicle’s rear suspension system, playing a vital role in handling, ride quality, and long-term durability. Designed to link the rear axle or hub assembly to the vehicle’s chassis, this suspension element ensures controlled wheel movement, optimal alignment, and balanced performance across diverse driving conditions—from daily commutes to aggressive cornering or off-road terrain.

Core Functions of the Rear Trailing Arm

Wheel Control and Ride Stability

The trailing arm acts as a pivot point that governs vertical wheel motion as the vehicle travels over bumps, dips, or uneven surfaces. By maintaining a stable connection between the chassis and the rear suspension, it allows the wheels to move up and down while minimizing lateral displacement.

This precise wheel control enhances traction and keeps the tires firmly planted on the road, significantly improving ride comfort and stability—especially on rough roads or during high-speed maneuvers. For the Subaru Legacy, known for its all-wheel-drive capability and balanced handling, this function is essential for delivering confident performance in all weather and road conditions.

Vehicle Balance and Lateral Stability

Rear trailing arms are instrumental in preventing unwanted side-to-side movement (also known as "axle steer") of the rear end. By constraining lateral motion, they help maintain directional stability and reduce the risk of oversteer or fishtailing, particularly during cornering, sudden lane changes, or emergency braking.

This role becomes even more critical under extreme conditions—such as wet roads, icy surfaces, or off-pavement driving—where maintaining rear-end composure is key to avoiding skidding or loss of control. In Subaru models, which emphasize safety and all-weather capability, the trailing arm contributes directly to predictable handling and driver confidence.

Connection Between Axle and Chassis

In independent rear suspension systems like those found on the Subaru Legacy, the trailing arm forms a structural link between the rear hub carrier (or axle) and the subframe. This connection allows controlled articulation of the wheel while supporting dynamic loads generated during acceleration, braking, and cornering.

Unlike solid axle setups, where trailing arms may allow lateral movement of the entire axle, in independent systems they guide motion along a defined path, ensuring smooth operation and minimizing stress on other suspension components such as bushings, ball joints, and CV axles. This design supports both performance and comfort by isolating road shocks effectively.

Wheel Alignment and Tension Management

Precise wheel alignment is critical for even tire wear, accurate steering response, and fuel efficiency. The rear trailing arm plays a direct role in maintaining proper toe and camber angles at the rear wheels. Some models feature adjustable trailing arms or eccentric bolts that allow technicians to fine-tune alignment settings during maintenance or after repairs.

When trailing arms wear out or become damaged, alignment shifts can occur, leading to rapid tire wear, pulling to one side, or a loose rear feel. Regular inspection ensures that suspension geometry remains within factory specifications, preserving tire life and overall vehicle dynamics.

Why the Subaru Rear Trailing Arm Matters

For Subaru owners, especially those with Legacy, Outback, or WRX models, the rear trailing arm is more than just a suspension link—it's a cornerstone of the brand’s renowned symmetrical all-wheel-drive system and balanced chassis dynamics. Because these vehicles are engineered for performance and all-weather reliability, every suspension component must perform at a high level.

Worn bushings, bent arms, or corroded mounting points can degrade handling, increase noise, and compromise safety. Therefore, routine inspection—especially after impacts like potholes or curbs—is highly recommended. Replacing trailing arms with OEM-spec or high-quality aftermarket parts ensures that suspension geometry and performance remain intact.

Important: If you notice vibrations, clunking sounds from the rear, or uneven tire wear, have your trailing arms and suspension system inspected by a qualified technician. Ignoring early signs of wear can lead to accelerated damage to tires, shocks, and other suspension components, resulting in higher repair costs and reduced safety.

Customization Options For Subaru Rear Trailing Arm

A rear trailing arm can be customized in numerous ways to enhance the performance of off-road vehicles, trucks, and SUVs—or to provide a more aggressive, refined aesthetic. These modifications are essential for improving strength, adjustability, handling precision, and durability under extreme conditions. Whether upgrading for rugged terrain or seeking a more responsive driving experience, selecting the right customization ensures optimal suspension behavior and long-term reliability.

Material Upgrades

The choice of material significantly impacts the trailing arm’s weight, strength, and longevity. Upgrading from stock components allows for better performance in demanding environments.

• Tubular Steel: Offers an excellent balance of strength and weight; commonly used in aftermarket performance arms due to its resistance to bending and ease of fabrication.
• Aluminum: Provides substantial weight savings while maintaining good corrosion resistance—ideal for reducing unsprung mass and improving ride responsiveness and fuel efficiency.
• Chromoly Steel: A high-strength alloy steel that is heat-treated for superior toughness and rigidity. Preferred in extreme off-road applications where maximum durability is required despite added weight.

Pro tip: Chromoly is often used in rock crawling and heavy-duty builds, while aluminum suits lightweight trail rigs and daily drivers needing improved agility.

Tubular vs. Solid Construction

The structural design of the trailing arm—whether tubular or solid—plays a critical role in both performance and visual appeal.

• Tubular Arms: Constructed from hollow steel or aluminum tubing, these arms are significantly lighter than solid counterparts, enhancing suspension articulation and overall vehicle handling. Their sleek, modern appearance also adds a custom, performance-oriented look.
• Solid Arms: Made from forged or CNC-machined billet metal, they offer maximum rigidity and are less prone to flex under heavy loads. Ideal for high-torque applications and severe off-road use, though at the cost of added weight.

Design insight: Tubular arms are favored in custom builds for their blend of function and style, while solid arms prioritize brute strength in commercial or competition-grade vehicles.

Mounting Points & Bushings

Upgrading the bushings and mounting hardware transforms how the rear axle responds to terrain, directly affecting ride quality and control.

• Stock Subaru Outback rear suspension parts use rubber bushings designed for comfort and noise absorption, but these can deflect under load, reducing precision.
• Polyurethane Bushings: Offer a middle ground—firmer than rubber, reducing deflection while still damping vibrations. Great for light off-roading and improved on-road handling.
• Spherical Bearings (Heim Joints): Provide zero deflection and maximum articulation, ideal for rock crawlers and race vehicles. However, they transmit more noise and vibration into the cabin.
• Reinforced mounting brackets or gusseted joints can prevent cracking under stress, especially after suspension lifts or increased engine power.

Key benefit: Upgraded bushings improve rear axle tracking, reduce wheel hop, and enhance traction on uneven surfaces.

Extended Trailing Arms

Extended arms are designed to accommodate lifted suspensions and increase rear axle travel for superior off-road capability.

• When a vehicle receives a suspension lift, stock trailing arms can cause improper driveline angles and limited wheel articulation.
• Extended arm suspension arms restore correct geometry, ensuring the axle moves smoothly through its range without binding.
• They allow for larger tires and better ground clearance while maintaining drivetrain safety and reducing U-joint wear.
• Often paired with adjustable links to fine-tune pinion angle and prevent vibrations.

Installation note: Always pair extended arms with a driveshaft inspection or upgrade to avoid premature failure due to altered angles.

Adjustable Trailing Arms

Adjustable arms offer unparalleled flexibility for tuning rear suspension alignment after modifications.

• Feature turnbuckle-style or threaded ends that allow precise length adjustments without replacing the entire arm.
• Enable correction of axle position, pinion angle, and toe settings—critical after installing lift kits, larger tires, or performance drivetrains.
• Popular in off-road racing and overlanding builds where suspension tuning is frequently needed based on terrain.
• Some models include jam nuts and locking collars to maintain settings under vibration and impact.

Smart upgrade: Adjustable arms save time and money during setup and allow real-time tuning for optimal traction and driveline health.

Finish & Aesthetic Enhancements

Beyond performance, customization includes visual upgrades that reflect personal style and protect against the elements.

• Powder Coating: Available in multiple colors (black, red, blue) to match vehicle themes; offers superior durability and rust resistance over paint.
• Zinc Plating or E-Coating: Corrosion-resistant finishes ideal for regions with snow, salt, or high humidity—perfect for Subaru owners in northern climates.
• Billet Aluminum Ends: Machined CNC ends with polished or anodized finishes add a high-end look and improved strength at stress points.

Bonus benefit: Protective coatings extend service life and reduce maintenance, especially in harsh environments.

Expert Recommendation: For most off-road enthusiasts, a combination of tubular chromoly arms with polyurethane bushings and slight extension offers the best balance of strength, articulation, and comfort. If maximum performance is the goal, consider fully adjustable arms with spherical bearings and a protective powder-coated finish. Always ensure compatibility with your Subaru model (e.g., Outback, Forester, or WRX) and consult fitment guides or VIN-based lookup tools before purchasing.

Additional Considerations

• Compatibility: Ensure custom arms are designed specifically for Subaru models (e.g., 2005–2025 Outback/Forester) to maintain OEM alignment specs.
• Warranty: Reputable brands offer limited lifetime warranties on materials and workmanship—look for this when investing in upgrades.
• Installation Complexity: Adjustable and extended arms may require professional alignment and driveline checks post-installation.
• Noise, Vibration, Harshness (NVH): High-performance bushings or bearings may increase cabin noise; consider driving environment when selecting.
• Federal & State Regulations: Modified suspension geometry must not violate local vehicle safety or emissions standards.

How To Choose The Subaru Rear Trailing Arm

Selecting the right rear trailing arm for your Subaru is a critical decision that directly impacts handling, durability, and overall performance. Whether you're upgrading for daily driving, spirited cornering, or off-road adventures, understanding the key factors—such as material construction, bushing type, adjustability, and environmental resistance—will ensure you make an informed choice tailored to your vehicle’s needs.

Safety & Compatibility Note: Always verify fitment with your specific Subaru model (e.g., WRX, Forester, Outback) and year. Incorrect trailing arms can compromise suspension geometry, leading to unsafe driving conditions and premature tire wear.

Key Factors in Choosing a Subaru Rear Trailing Arm

1. Define Your Driving Application
   • On-Road / Daily Driving: Prioritize comfort and longevity. OEM-style replacements or mild upgrades with rubber bushings are ideal for maintaining ride quality.
   • Performance / Track Use: Opt for arms with spherical bearings or polyurethane bushings to minimize deflection, improve responsiveness, and enhance cornering precision.
   • Off-Road / Rally Applications: Choose heavy-duty arms made from forged aluminum or chromoly steel. These offer superior strength, impact resistance, and fatigue durability under extreme conditions.
2. Material & Construction Quality
   • High-quality aftermarket arms are often made from 6061-T6 or 7075 aluminum, offering an excellent strength-to-weight ratio while resisting corrosion.
   • For extreme durability, look for heat-treated steel arms used in rally builds, though they add weight.
   • Avoid thin-walled or poorly welded arms. Inspect product photos and manufacturer specifications for wall thickness and reinforcement details.
3. Bushing Type and Performance Impact
   • Rubber Bushings: Found in stock arms, they absorb vibrations and road noise, providing a smooth, quiet ride. However, they deform under load, reducing handling accuracy.
   • Polyurethane Bushings: A popular upgrade offering firmer support than rubber with improved longevity and reduced flex. Slightly stiffer ride but better feedback and control.
   • Spherical Bearings (Heim Joints): Used in performance and off-road setups. Provide zero deflection and maximum articulation but transmit more noise and vibration into the cabin. Require regular maintenance.
4. Corrosion Resistance & Finish
   • Subarus, especially those in snowy or coastal climates, are prone to rust. Choose trailing arms with a powder-coated finish or anodized aluminum construction for superior protection.
   • Stainless steel hardware should be included or recommended to prevent seized bolts during future service.
   • Sealed bushings or greaseable spherical joints help keep dirt and moisture out, extending service life.
5. Hardware & Fastener Quality
   • Inferior bolts can stretch or fail under stress. Ensure the kit includes grade 8.8 or higher metric fasteners (or equivalent ASTM standards).
   • Look for kits with locknuts, threadlocker-ready bolts, or Nyloc nuts to prevent loosening from vibration.
   • Complete kits often include alignment shims or eccentric washers for adjustability—especially useful when correcting rear toe after lift or suspension modifications.
6. Adjustability & Alignment Features
   • Some aftermarket arms offer eccentric bushings or slotted mounting points to allow fine-tuning of rear toe and camber.
   • This is particularly beneficial after lifting the vehicle or installing performance suspension components.
   • Adjustable arms can extend tire life by enabling precise alignment settings that compensate for modified geometry.

Expert Tip: After installing new trailing arms, always perform a full rear suspension alignment. Even slight changes in toe or camber can lead to rapid tire wear and compromised handling. Use a shop familiar with Subaru’s multi-link rear suspension for best results.

Maintenance & Long-Term Considerations

• Inspect trailing arm bushings every 15,000 miles for cracks, tears, or excessive play.
• Lubricate greaseable spherical joints every 5,000 miles or with each oil change in dusty environments.
• Check mounting bolts for tightness after the first 500 miles of driving, especially on off-road or performance arms.
• Consider upgrading both left and right arms simultaneously to ensure balanced handling and wear.
• Pair new trailing arms with upgraded rear lateral links or toe arms for a complete performance suspension refresh.

Choosing the right Subaru rear trailing arm isn’t just about strength—it’s about matching the component to your driving style, environment, and performance goals. Whether you're maintaining your daily driver or building a rally-ready machine, investing in high-quality, properly specified trailing arms ensures safer handling, longer component life, and a more rewarding driving experience. When in doubt, consult a Subaru specialist or suspension professional to confirm compatibility and installation requirements.

Frequently Asked Questions About Trailing Arms

A failing trailing arm can compromise both vehicle safety and ride quality. Since trailing arms are critical components of the suspension system that maintain proper axle alignment and wheel geometry, their deterioration often leads to noticeable performance issues. Key warning signs include:

• Uneven Tire Wear: Misaligned wheels due to a bent or loose trailing arm cause irregular tread wear, especially on one side of the tire.
• Poor Vehicle Handling: The car may pull to one side, wander on straight roads, or feel unstable during turns.
• Clunking or Knocking Noises: Especially when driving over bumps or potholes, caused by worn bushings or loose mounting points.
• Shaky Suspension Feel: Excessive vibration or wobbling from the rear of the vehicle, particularly at higher speeds.
• Visible Damage: Cracks, bends, or corrosion on the trailing arm itself, or visibly compressed or split rubber bushings.

If any of these symptoms are present, it's crucial to have the suspension inspected by a qualified technician. Delaying repairs can lead to accelerated wear on tires, shocks, and other suspension components—and increases the risk of loss of control in emergency maneuvers.

Yes, while heavy-duty or solid trailing arms offer increased durability—especially beneficial for off-road or high-stress applications—they can impact on-road performance in certain ways:

• Reduced Flex and Articulation: Stiffer materials like forged steel or solid aluminum limit suspension flex, which can reduce wheel travel and traction on uneven surfaces when used off-road, but more importantly, lead to a harsher ride on paved roads.
• Decreased Ride Comfort: Compared to stock or performance-tuned arms with compliant bushings, rigid setups transmit more road vibrations into the cabin.
• Altered Handling Dynamics: Overly stiff arms may change the suspension’s natural movement, potentially affecting cornering stability and responsiveness.
• Increased Stress on Mounts: Excessive rigidity can transfer more force to frame mounting points, possibly leading to premature bushing wear or even frame damage over time.

For daily drivers or highway-focused vehicles, it's recommended to choose trailing arms that balance strength with ride quality—such as those with polyurethane bushings or tuned flex characteristics—rather than full solid replacements designed strictly for extreme off-road use.

Installing rear trailing arms on a Subaru (such as models from the WRX, STI, Legacy, or Outback series) is a moderately complex job that requires mechanical experience, proper tools, and attention to alignment specifications. While possible for advanced DIYers, professional installation is strongly advised to ensure safety and performance.

General Installation Steps:

1. Lift and Secure the Vehicle: Use a floor jack and jack stands to safely raise the rear of the car. Remove the rear wheels for access.
2. Support the Rear Axle: Use a jack or support stand to prevent the differential or axle from dropping once the arms are removed.
3. Remove Old Trailing Arms: Disconnect the mounting bolts at both the chassis and axle ends. Pay close attention to the condition of bushings and hardware—replace worn components as needed.
4. Install New Arms: Position the new trailing arms and secure them using manufacturer-recommended torque specifications. Ensure bushings are properly seated and not twisted.
5. Adjust Length and Alignment (if applicable): Adjustable arms may require setting the correct length to maintain proper pinion angle and rear toe alignment.
6. Reassemble and Torque: Reinstall all hardware and torque to spec, typically with the vehicle’s weight on the suspension to prevent pre-loading bushings.

Post-Installation: A professional alignment is essential. Incorrect setup can lead to rapid tire wear, poor handling, or driveline vibrations. Always refer to your vehicle’s service manual or the arm manufacturer’s instructions for model-specific procedures.

Absolutely—adjustable trailing arms are a game-changer for off-road vehicles, particularly those modified with lift kits or used in extreme terrain. Their ability to fine-tune suspension geometry makes them a vital upgrade for serious off-road enthusiasts.

Key Benefits for Off-Road Use:

• Pinion Angle Adjustment: After a suspension lift, the differential’s angle can shift, causing driveline vibrations or u-joint wear. Adjustable arms allow precise correction of the pinion angle for smooth power delivery.
• Improved Axle Centering: Helps keep the rear axle properly aligned under the chassis, preventing lateral movement and enhancing stability on rough trails.
• Customizable Wheelbase and Articulation: Enables tuning of wheel travel and suspension flex for maximum traction in rock crawling or uneven terrain.
• Compatibility with Modifications: Works seamlessly with lifted suspensions, larger tires, and aftermarket differentials without compromising geometry.
• Long-Term Flexibility: Future upgrades or terrain-specific setups can be accommodated by simply readjusting the arms instead of replacing them.

Whether you're building a trail rig or modifying a Subaru for rally-inspired off-road adventures, adjustable trailing arms provide the control and adaptability needed to optimize performance, durability, and safety beyond factory limitations.